White kidney bean extract: how to choose it and how to take it

The white bean is familiar in every Bulgarian kitchen, but the extract made from it is a completely different product from the beans in the pot. What is valuable in it is a single protein — and for that protein to stay active, the raw material has to be processed with care. Here is how to choose a good extract, and why.

How to choose

• Standardised by activity — in units per gram (for example ≥3000 U/g), not just “extract”.
• A stated ratio — 10:1 means 10 kg of beans for 1 kg of extract.
• Gentle processing that preserves the active protein.
• A clear daily dose in mg, from which you can work out the activity units.
• A certificate of analysis for the batch — activity, heavy metals, microbiology.

Why? Read on.

Why units, not percentages

The bean's alpha-amylase inhibitor is a protein, and a protein is valuable only for as long as it keeps its shape. The percentage of protein in an extract does not tell you whether it is active — two extracts with the same amount of protein can differ many times over. Bean varieties also differ in their content of the individual forms of the inhibitor.

That is why quality is measured in the laboratory: starch, the enzyme alpha-amylase and the sample are mixed, and the amount of the enzyme's activity that has been blocked is measured. The result is expressed in units per gram — “≥3000 U/g” means at least 3000 such units in every gram of extract.

Found in:Metabolic Complex ·Metabolic Complex Caffeine-Free

What 10:1 means

A ratio of 10:1 means that 10 parts of dry beans yield 1 part of extract. So 1500 mg of extract corresponds to about 15 g of beans, and 1800 mg to about 18 g. The ratio tells you how much raw material stands behind the extract, and the activity tells you how much of the valuable protein has been preserved. Together they give the full picture.

Why processing matters

The inhibitor is sensitive to heat: boiled at 100 °C for 10 minutes, its activity is lost completely. That is why cooked beans and bean extract are different things. Raw beans, however, also contain natural lectins, which are neutralised by heat treatment. A good manufacturer finds the balance — controlled temperatures at which the lectins are reduced while the inhibitor stays active — and checks the result by analysis.

The dose in milligrams

Once you know the dose in mg and the activity per gram, the sum is easy: 1500 mg of extract at ≥3000 U/g gives at least 4500 units a day, and 1800 mg gives at least 5400.

The certificate of analysis

A good certificate confirms the activity in U/g, the ratio, the heavy metals and the microbiological purity. The certificate of analysis for each of our batches is on the product page and behind the QR code on the packaging.

The plant

The common bean (Phaseolus vulgaris) is native to the Americas. Its wild forms grow in Mesoamerica and in the Andes, and it was domesticated at least twice, independently, in the two regions. It arrived in Europe after Columbus's voyages: the first reliable records are of Andean varieties, probably brought to Spain after Pizarro's expedition to Peru in 1529, while the first Mesoamerican variety was described in 1542. From there the bean spread quickly across Europe.

Phaseolamin

In 1975, Marshall and Lauda purified from the bean a protein inhibitor of alpha-amylase and named it phaseolamin. Today we know that its main form (αAI-1) is a glycoprotein of about 43 kDa, made up of two pairs of α and β chains. The plant makes it as an inactive precursor, which in mature seeds splits into the two chains. The inhibitor belongs to the lectin family — proteins that bind carbohydrates. Another of its forms, αAI-2, targets the enzyme of one species of bean weevil — part of the seed's natural defence.

White kidney bean in Metabolic Complex

Metabolic Complex contains 1500 mg of white kidney bean extract 10:1 (≥3000 U/g) a day, and Metabolic Complex caffeine-free contains 1800 mg. The authorised health claims for the formula come from the minerals in it — for example from chromium (100 µg, 250% NRV):

• Chromium contributes to normal macronutrient metabolism.
• Chromium contributes to the maintenance of normal blood glucose levels.

How to take it

White kidney bean extract is taken with food.

• Metabolic Complex: 3 capsules with breakfast and 3 with lunch, not in the evening. Contains caffeine (150 mg a day) — not recommended for children and pregnant women.
• Metabolic Complex caffeine-free: 2 capsules with each of the three meals.

Both products contain 300 mg of EGCG a day — do not take them on an empty stomach or on the same day as other green tea products. Not suitable for pregnant or breastfeeding women or for anyone under 18.